1. Field of the Invention
The present invention relates to a loudspeaker system, and more particularly to an improvement in a loudspeaker cabinet or enclosure of the bass-reflex type.
2. Discussion of the Prior Art
Loudspeaker systems of the bass-reflex design, such as shown in FIGS. 1A and 1B or FIGS. 2A and 2B of the accompanying drawings, have a cabinet or enclosure 10 in which loudspeakers 11 and 12 are mounted, sound waves radiating from the back of the loudspeaker cones within the cabinet being emitted out through a hollow rectangular parallelopipedal duct or port 13, or a hollow cylindrical duct or port 14 supported in the cabinet 10, in which duct the phase of the sound waves is reversed.
With the conventional bass-reflex loudspeaker systems, there are produced in the ducts standing waves which make mid-range sounds unclear or cause peaks and dips to appear in the frequency characteristic. With a hollow rectangular parallelopipedal duct 13 dimensioned as shown in FIG. 3, for example, the frequencies of such standing waves can be calculated as follows: EQU f.sub.1 = C/2l.sub.1, f.sub.2 = C/2l.sub.2, f.sub.3 = C/2l.sub.3
in which
L.sub.1 = length [m] of the duct; PA1 L.sub.2 = width [m] of the duct; PA1 L.sub.3 = height [m] of the duct; and PA1 C = speed [m/sec.] of sound in air
As illustrated in FIG. 4, these standing waves f.sub.1, f.sub.2 and f.sub.3 generate peaks and dips at different frequencies in the frequency response curve. It is known that among these standing waves, the one having the frequency f.sub.1, which is generated in the longitudinal direction of the duct, most adversely affects the frequency characteristic of the system.